A green potassium citrate activation strategy via one-step synthesis of 3D porous carbon for capacitive deionization

Abstract

Capacitive deionization (CDI) shows potential for desalination whereas exploring green and low-cost porous carbon electrodes exhibiting good desalination performance is still challenging. Herein, a green one-step carbonization-activation strategy was developed with carboxymethyl cellulose (CMC) as precursor and potassium citrate as activator to prepare CA(K)/CMC for CDI desalination. Owing to the introduction of potassium citrate, CA(K)/CMC exhibited larger specific surface area, better porous structure, more defects, and richer oxygen content. These improvements effectively accelerated charge transfer and ion transport process in CA(K)/CMC, which significantly increased the specific capacitance of CA(K)/CMC. Owing to the synergistic effect of these above properties, the optimized CA(K)/CMC-1-2 demonstrated high salt adsorption capacity (17.21 mg g−1, 1.2 V, 200 mg/L) and desalination rate (0.023 mg g−1 s−1, 1.2 V, 200 mg/L), and good cycling stability. Density functional theory (DFT) calculations further verified the advantageous characteristics of CA(K)/CMC-1-2 indeed improved ions adsorption. This finding offers new insights for designing green and economical carbon-based electrodes for desalination by CDI.